The development of synthetic methodologies for the introduction of sulfurpentafluoride or pentafluorosulfuranyl groups (“SF5”) into organic compounds has been pursued with a considerable degree of interest. The SF5 groups impart unique properties to these organic compounds that include, inter alia, low surface energy, high chemical resistance, high thermal stability, high electronegativity, hydrophobicity, and high dielectric constant. The high electronegativity value of the SF5 group, 3.62 on the Pauling scale, and its greater electron withdrawing ability makes it an attractive alternative for the trifluoromethyl group (“CF3”) found in many commercial products.
Organic compositions containing SF5 have been used in a variety of applications. For example, pentafluorosulfuranyl fluoroaliphatic compositions have been used as surfactants, mono and bis (pentafluorosulfur)-substituted diacetylenes have been used to prepare SF5-containing polymers, sulfur pentafluorophenyl pyrazoles have been suggested for the control of ecoparasitic infections, and sulfurpentafluoride derivatives have been used to prepare liquiderystal media. Thus, there is an interest in efficient methods for the introduction of the SF5 group into a variety of compounds.
The following articles and patents are representative of methods for introducing SF5 groups into organic compounds.
U.S. Pat. No. 4,535,011 discloses a process for producing mono (pentafluorosulfur diacetylene polymers wherein sulfur pentafluoro bromide is first reacted with acetylene at temperatures below about −70° C., and then, the resulting intermediate debrominated. Dehydrobromination is effected by reacting the intermediate adduct with a strong base, e.g., potassium hydroxide.
U.S. Pat. No. 6,479,645 discloses methods for producing sulfurpentafluoride compounds having a substituted silyl group. In the disclosed process, sulfur pentafluoro bromide is reacted with a trisubstituted silyl acetylene in the presence of potassium fluoride at room temperature. Bromine is removed from the intermediate compound by addition of powdered potassium hydroxide.
The article, New and Convenient Method for Incorporation of Pentafluorosulfanyl (SF5) Substituents Into Aliphatic Organic Compounds, Samai Ayt-Mohand and W. Dolbier, Organic Letters, 2002, 4,17, 3013 discloses the addition of the SF5-group to organic compounds by the reaction of SF5Cl with alkynes and alkenes in the presence of triethylborane and hexane solvent at temperatures from −30° C. to room temperature.
In the article, New SF5-Long Chain Carbon Systems, R. Winter and G. L. Gard, Inorganic Chemistry, Journal of Fluorine Chemistry, 107 (2001) 23-30, sulfur pentafluoro chloride is reacted with a terminal olefin, e.g., 1-hexene and 9-decyl-1-acetate to produce an intermediate in the formation of SF5-terminated perfluoroalkyl thiols. The authors note that the reaction of sulfur pentafluoro bromine is too reactive with 1-hexene and only BrF adducts are found by GC analysis.
In the article, The —SF5, SeF5, and TeF5 Groups In Organic Chemistry, D. Lentz and K. Seppelt, Chemistry of Hypervalent compounds© 1999 Wiley-VCH, Inc, p. 295-325, there is disclosed the addition of the SF5 group into organic compounds by reaction with S2F10, SF5OF, SF5Cl, and SF5Br. Successful addition of SF5Br to alkynes and fluoroalkenes was reported. It was reported also that SF5Br added in cases where SF5Cl failed and SF5Cl added in cases where SF5Br did not.
The article, Functionalization of Pentafluoroe-λ6-Sulfanyl (SF5) Olefins and Acetylenes, Winter and Gard, et al, American Chemical Society, ©1994 128-147 discloses the preparation of SF5 derivatives of alkynes and alkenes. In one example SF5X addition to alkenes can be moderated by working either in the gas phase, (ethylene and SF5Br), operating at low temperatures (−110° C.) or the reaction carried out at high dilution in an inert solvent.